/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* @(#)e_remainder.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/* __ieee754_remainder(x,p)
 * Return :
 * 	returns  x REM p  =  x - [x/p]*p as if in infinite
 * 	precise arithmetic, where [x/p] is the (infinite bit)
 *	integer nearest x/p (in half way case choose the even one).
 * Method :
 *	Based on fmod() return x-[x/p]chopped*p exactlp.
 */

#ifdef POK_NEEDS_LIBMATH
#include "math_private.h"
#include <libm.h>

static const double zero = 0.0;

double __ieee754_remainder(double x, double p) {
  int32_t hx, hp;
  uint32_t sx, lx, lp;
  double p_half;

  EXTRACT_WORDS(hx, lx, x);
  EXTRACT_WORDS(hp, lp, p);
  sx = hx & 0x80000000;
  hp &= 0x7fffffff;
  hx &= 0x7fffffff;

  /* purge off exception values */
  if ((hp | lp) == 0)
    return (x * p) / (x * p); /* p = 0 */
  if ((hx >= 0x7ff00000) ||   /* x not finite */
      ((hp >= 0x7ff00000) &&  /* p is NaN */
       (((hp - 0x7ff00000) | lp) != 0)))
    return (x * p) / (x * p);

  if (hp <= 0x7fdfffff)
    x = __ieee754_fmod(x, p + p); /* now x < 2p */
  if (((hx - hp) | (lx - lp)) == 0)
    return zero * x;
  x = fabs(x);
  p = fabs(p);
  if (hp < 0x00200000) {
    if (x + x > p) {
      x -= p;
      if (x + x >= p)
        x -= p;
    }
  } else {
    p_half = 0.5 * p;
    if (x > p_half) {
      x -= p;
      if (x >= p_half)
        x -= p;
    }
  }
  GET_HIGH_WORD(hx, x);
  SET_HIGH_WORD(x, hx ^ sx);
  return x;
}
#endif
